1. Field of the Invention
The present invention relates to an apparatus for monitoring a condition of blood circulation of a living subject.
2. Related Art Statement
There is known a circulation-condition monitoring apparatus which includes a heartbeat-synchronous-wave detecting device which is worn on a patient and detects a heartbeat-synchronous wave from the subject; an arrhythmia judging means for judging whether an arrhythmia has occurred to the patient, based on the heartbeat-synchronous wave detected by the heartbeat-synchronous-wave detecting device; and an alarming device which produces an alarming sound when the arrhythmia judging means judges that an arrhythmia has occurred to the patient. For example, there is known a circulation-condition monitoring apparatus which includes an electrocardiograph (i.e., heartbeat-synchronous-wave detecting device) having a plurality of electrodes adapted to be worn at a plurality of prescribed locations on a living subject to detect an electrocardiogram as a heartbeat-synchronous wave; an arrhythmia diagnosing means for automatically diagnosing an arrhythmia of the subject based on the electrocardiogram detected by the electrocardiograph; and an alarming device which produces an alarming sound when it is judged that an arrhythmia has occurred to the subject.
Since an arrhythmia may indicate that the circulation condition of a patient has worsened, the conventional circulation-condition monitoring apparatus produces an alarming sound when it judges that an arrhythmia has occurred to the patient. However, in some cases, an arrhythmia does not indicate that the circulation condition of a patient has worsened. Therefore, if the monitoring apparatus produces an alarming sound each time it judges that an arrhythmia has occurred to a patient, there will be some cases where an alarming sound is produced when the circulation condition of a patient has not worsened. If those cases are too frequent, a medical staff may keep the alarming device turned off. On the other hand, in other cases, an arrhythmia does indicate that the circulation condition of a patient has worsened. Thus, it is not recommended to keep the alarming device off.
Meanwhile, the circulation condition of a patient can be monitored based on his or her blood pressure. Hence, there had been proposed an automatic blood-pressure monitoring apparatus which continuously monitors whether an arrhythmia has occurred to a patient and, when an arrhythmia has occurred to a patient, automatically measures a blood pressure of the patient. An example of this automatic blood-pressure monitoring apparatus is an automatic blood-pressure measuring apparatus disclosed in Japanese Utility Model Application laid open under Publication No. 64-56206. The disclosed automatic blood-pressure measuring apparatus automatically measures, when it is judged that an arrhythmia has occurred to a patient, a blood pressure of the patient, and judges whether the measured blood pressure falls within a prescribed reference range. Since the prior apparatus monitors the circulation condition of a patient based on both arrhythmia and blood pressure, it can considerably accurately monitor the same.
However, there are some cases where, in a state in which an arrhythmia has occurred to a patient, a blood pressure whose value is normal in a state in which the patient has no arrhythmia indicates, in fact, that the patient needs an urgent treatment. That is, there are some cases where the automatic blood-pressure measuring apparatus disclosed in the above-indicated document does not judge that an abnormality has occurred to a patient but, in fact, the circulation condition of the patient is abnormal and the patient needs an argent treatment. Thus, the accuracy with which the automatic blood-pressure measuring apparatus monitors the circulation condition of the patient is not sufficiently high.
It is therefore an object of the present invention to provide a blood-circulation monitoring apparatus which can accurately monitor a condition of blood circulation of a living subject.
The Inventor has carried out extensive studies, and has found that if an arrhythmia is caused by an abnormal circulation condition of a living subject, then the blood pressure of the subject exhibits a great change. Therefore, an abnormal circulation condition of the subject can be accurately identified if an arrhythmia is found and simultaneously the blood pressure of the subject exhibits a great change, even if the blood pressure may not exhibit an abnormal value.
In addition, the Inventor has found that an abnormal circulation condition of a living subject can be accurately identified by employing, when an arrhythmia is present, a reference range whose upper and/or lower limit(s) are/is nearer to a normal blood pressure value than the upper and/or lower limits of a reference range which is employed when no arrhythmia is present.
The above object has been achieved by the present invention. According to a first feature of the present invention, there is provided an apparatus for monitoring a condition of blood circulation of a living subject, comprising a heartbeat-synchronous-wave detecting device which detects a heartbeat-synchronous wave from the subject; an arrhythmia judging means for judging whether an arrhythmia has occurred to the subject, based on the heartbeat-synchronous wave detected by the heartbeat-synchronous-wave detecting device; a first blood-pressure determining means including an inflatable cuff which is adapted to be wound around a first body portion of the subject to occlude an artery of the first body portion, the first blood-pressure determining means determining at least one first blood pressure of the subject based on a first pulse wave which is produced in the cuff when a pressure in the cuff is decreased; a blood-pressure-relating-information obtaining means including at least one pulse-wave detecting device which is adapted to be worn on at least one second body portion of the subject to detect at least one second pulse wave from the at least one second body portion without occluding at least one artery of the at least one second body portion, the blood-pressure-relating-information obtaining means iteratively obtaining, based on the at least one second pulse wave detected by the at least one pulse-wave detecting device, a piece of blood-pressure-relating information which changes in relation with blood pressure of the subject; a relationship determining means for determining a relationship between blood pressure and blood-pressure-relating information, based on at least one first blood pressure value determined by the first blood-pressure determining means and at least one piece of blood-pressure-relating information obtained by the blood-pressure-relating-information obtaining means; a second blood-pressure determining means for iteratively determining, according to the relationship determined by the relationship determining means, a second blood pressure of the subject based on each of the pieces of blood-pressure-relating information iteratively obtained by the blood-pressure-relating-information obtaining means; a change-value calculating means for calculating a change value of each of the second blood pressure values iteratively determined by the second blood-pressure determining means; and an abnormality judging means for judging that the condition of blood circulation of the subject is abnormal, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject and when the change value calculated by the change-value calculating means does not fall within a first reference range.
In the present circulation-condition monitoring apparatus, the change-value calculating means calculates a change value of each of the second blood pressure values iteratively determined by the second blood-pressure determining means, and the abnormality judging means judges that the condition of blood circulation of the subject is abnormal, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject and when the change value calculated by the change-value calculating means does not fall within a first reference range. Thus, the present apparatus can accurately monitor the circulation condition of the subject. In addition, the pieces of blood-pressure-relating information can be obtained based on the second pulse wave detected by the pulse-wave detecting device without occluding the artery of the second body portion of the subject, and the second blood pressure values are determined based on the pieces of blood-pressure-relating information. Thus, the present apparatus is free of the disadvantage that each time it is judged that an arrhythmia has occurred to the subject, the first blood pressure determining means is operated to occlude the artery of the first body portion of the subject and thereby cause the subject to feel discomfort.
According to a second feature of the present invention that includes the above-described first feature, the circulation-condition monitoring apparatus further comprises an input device which is operable for inputting a low-blood-pressure-subject signal indicating that the blood pressure of the living subject is low, and the abnormality judging means judges, when the low-blood-pressure-subject signal is input through the input device, that the condition of blood circulation of the subject is abnormal, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject and when at least one of the change value calculated by the change-value calculating means and said each second blood pressure value determined by the second blood-pressure determining means does not fall within a corresponding one of the first reference range and a second reference range. A low-blood-pressure subject exhibits a low blood pressure even when his or her circulation condition may be normal. Therefore, there are some cases where the blood pressure of the subject is so low as to need an urgent treatment even if the change of the blood pressure may not be so great. In the present circulation-condition monitoring apparatus, if the low-blood-pressure-subject signal is input through the input device, then the abnormality judging means judges that the condition of blood circulation of the subject is abnormal, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject and when at least one of the change value calculated by the change-value calculating means and the each second blood pressure value determined by the second blood-pressure determining means does not fall within a corresponding one of the first reference range and a second reference range. Thus, the present apparatus can reliably judge an abnormality of the circulation condition of the subject whose blood pressure is low.
According to a third feature of the present invention, there is provided an apparatus for monitoring a condition of blood circulation of a living subject, comprising a heartbeat-synchronous-wave detecting device which detects a heartbeat-synchronous wave from the subject; an arrhythmia judging means for judging whether an arrhythmia has occurred to the subject, based on the heartbeat-synchronous wave detected by the heartbeat-synchronous-wave detecting device; a blood-pressure measuring means including an inflatable cuff which is adapted to be wound around a body portion of the subject, and iteratively measuring a blood pressure of the subject based on a pulse wave which is produced in the cuff when a pressure in the cuff is changed; a change-value calculating means for iteratively calculating a change value of each of the blood pressure values iteratively measured by the blood-pressure measuring means; and an abnormality judging means for operating, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject, the blood-pressure measuring means to measure a blood pressure of the subject, and the change-value calculating means to calculate a change value of the measured blood pressure value, and judging that the condition of blood circulation of the subject is abnormal, when the change value calculated by the change-value calculating means does not fall within a first reference range.
In the present circulation-condition monitoring apparatus, the abnormality judging means operates, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject, the blood-pressure measuring means to measure a blood pressure of the subject, and the change-value calculating means to calculate a change value of the measured blood pressure value, and judges that the condition of blood circulation of the subject is abnormal, when the change value calculated by the change-value calculating means does not fall within a first reference range. Thus, based on both arrhythmia and blood-pressure change, the present apparatus judges an abnormality of the circulation condition of the subject. Accordingly, the present apparatus can monitor the circulation condition of the subject.
According to a fourth feature of the present invention that includes the above-described third feature, the circulation-condition monitoring apparatus further comprises an input device which is operable for inputting a low-blood-pressure-subject signal indicating that the blood pressure of the living subject is low, and the abnormality judging means operates, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject, the blood-pressure measuring means and the change-value calculating means, and judges that the condition of blood circulation of the subject is abnormal, when at least one of the change value calculated by the change-value calculating means and the blood pressure value measured by the blood-pressure measuring means does not fall within a corresponding one of the first reference range and a second reference range. In the present circulation-condition monitoring apparatus, if the low-blood-pressure-subject signal is input through the input device, then the abnormality judging means operates, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject, the blood-pressure measuring means and the change-value calculating means, and judges that the condition of blood circulation of the subject is abnormal, when at least one of the change value and the blood pressure value does not fall within a corresponding one of the first reference range and the second reference range. Thus, the present apparatus can reliably judge an abnormality of the circulation condition of the subject whose blood pressure is low.
According to a fifth feature of the present invention, there is provided an apparatus for monitoring a condition of blood circulation of a living subject, comprising a heartbeat-synchronous-wave detecting device which detects a heartbeat-synchronous wave from the subject; an arrhythmia judging means for judging whether an arrhythmia has occurred to the subject based on the heartbeat-synchronous wave detected by the heartbeat-synchronous-wave detecting device; a blood-pressure measuring means including an inflatable cuff which is adapted to be wound around a body portion of the subject, and measuring a first blood pressure of the subject based on a pulse wave which is produced in the cuff when a pressure in the cuff is changed; a first abnormality judging means for judging that the condition of blood circulation of the subject is abnormal, when the first blood pressure value measured by the blood-pressure measuring means is not greater than a first reference value; and a second abnormality judging means for operating, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject, the blood-pressure measuring means to measure a second blood pressure of the subject, and judging that the condition of blood circulation of the subject is abnormal, when the second blood pressure value measured by the blood-pressure measuring means is not greater than a second reference value greater than the first reference value.
In present circulation-condition monitoring apparatus, the first abnormality judging means judges that the condition of blood circulation of the subject is abnormal, when the first blood pressure value measured by the blood-pressure measuring means is not greater than a first reference value. In addition, even if the first abnormality judging means does not judge that the condition of blood circulation of the subject is abnormal, the second abnormality judging means operates, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject, the blood-pressure measuring means to measure a second blood pressure of the subject, and judges that the condition of blood circulation of the subject is abnormal, when the second blood pressure value measured by the blood-pressure measuring means is not greater than a second reference value greater than the first reference value. Thus, the present apparatus can accurately judge an abnormality of the circulation condition of the subject.
According to a sixth feature of the present invention, there is provided an apparatus for monitoring a condition of blood circulation of a living subject, comprising a heartbeat-synchronous-wave detecting device which detects a heartbeat-synchronous wave from the subject; an arrhythmia judging means for judging whether an arrhythmia has occurred to the subject based on the heartbeat-synchronous wave detected by the heartbeat-synchronous-wave detecting device; a first blood-pressure determining means including an inflatable cuff which is adapted to be wound around a first body portion of the subject to occlude an artery of the first body portion, the first blood-pressure determining means determining at least one first blood pressure of the subject based on a first pulse wave which is produced in the cuff when a pressure in the cuff is decreased; a blood-pressure-relating-information obtaining means including at least one pulse-wave detecting device which is adapted to be worn on at least one second body portion of the subject to detect at least one second pulse wave from the at least one second body portion without occluding at least one artery of the at least one second body portion, the blood-pressure-relating-information obtaining means iteratively obtaining, based on the at least one second pulse wave detected by the at least one pulse-wave detecting device, a piece of blood-pressure-relating information which changes in relation with blood pressure of the subject; a relationship determining means for determining a relationship between blood pressure and blood-pressure-relating information, based on at least one first blood pressure value determined by the first blood-pressure determining means and at least one piece of blood-pressure-relating information obtained by the blood-pressure-relating-information obtaining means; a second blood-pressure determining means for iteratively determining, according to the relationship determined by the relationship determining means, a second blood pressure of the subject based on each of a plurality of pieces of blood-pressure-relating information iteratively obtained by the blood-pressure-relating-information obtaining means; a first abnormality judging means for judging that the condition of blood circulation of the subject is abnormal, when a first blood pressure value determined by the first blood-pressure determining means is not greater than a first reference value; and a second abnormality judging means for judging that the condition of blood circulation of the subject is abnormal, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject and when a second blood pressure value determined by the second blood-pressure determining means is not greater than a second reference value greater than the first reference value.
In present circulation-condition monitoring apparatus, the first abnormality judging means judges that the condition of blood circulation of the subject is abnormal, when the first blood pressure value measured by the blood-pressure measuring means is not greater than a first reference value. In addition, even if the first abnormality judging means does not judge that the condition of blood circulation of the subject is abnormal, the second abnormality judging means judges that the condition of blood circulation of the subject is abnormal, when the arrhythmia judging means judges that the arrhythmia has occurred to the subject and when the second blood pressure value measured by the second blood-pressure determining means is not greater than a second reference value greater than the first reference value. Thus, the present apparatus can accurately monitor the circulation condition of the subject. In addition, the pieces of blood-pressure-relating information can be obtained based on the second pulse wave detected by the pulse-wave detecting device without occluding the artery of the second body portion of the subject, and the second blood pressure values are determined based on the pieces of blood-pressure-relating information. Thus, the present apparatus is free of the disadvantage that each time it is judged that an arrhythmia has occurred to the subject, the first blood pressure determining means is operated to occlude the artery of the first body portion of the subject and thereby cause the subject to feel discomfort.
According to a seventh feature of the present invention that includes any of the above-described first to sixth features, the heartbeat-synchronous-wave detecting device comprises an electrocardiograph which includes a plurality of electrodes that are adapted to be worn at a plurality of prescribed locations on the living subject and which detects, as the heartbeat-synchronous wave, an electrocardiogram through the electrodes. In this apparatus, the electrocardiograph detects electrocardiogram of the subject, and the arrhythmia judging means judges, based on the detected electrocardiogram, whether an arrhythmia has occurred to the subject. Thus, the arrhythmia judging means can identify various sorts of arrhythmias.
According to an eighth feature of the present invention that includes any of the above-described first to sixth features, the heartbeat-synchronous-wave detecting device comprises the inflatable cuff and detects, as the heartbeat-synchronous wave, the pulse wave which is produced in the cuff in a state in which the pressure in the cuff is equal to a pre-set value lower than a diastolic blood pressure value of the living subject. In this apparatus, the cuff as part of the first blood-pressure determining means is used to detect the heartbeat-synchronous wave. Thus, the present circulation-condition monitoring apparatus can enjoy a simple construction, and can be produced at reduced cost.